1. Field of the Invention
The present invention generally relates to a bilateral filter, and more particularly to fast bilateral filtering using a bilateral histogram.
2. Description of Related Art
A bilateral filter is a nonlinear edge preserving filter that smooths an image while preserving edges. The intensity value at each pixel in the image is replaced by a weighted average of intensity values from nearby pixels. It has demonstrated great effectiveness for many computer vision and computer graphics problems such as tone mapping, demosaicking and low-light enhancement.
The bilateral filer is a nonlinear combination of spatial and range filters. Implementing the bilateral filter is computationally intensive owing to the nonlinearity of the range filter. Conventional techniques are proposed to speed up bilateral filtering either by confining the spatial kernel or numerical approximation. The memory cost for the conventional bilateral filtering can be unacceptable large for small kernel size.
A need has thus arisen to propose a novel scheme to overcome drawbacks of the conventional bilateral filters.